Outdoor testing of agricultural cladding materials

In this research, optical and mechanical properties of three different types of (polyethylene) PE plastic films commonly used for cladding greenhouse in TURKEY were studied. The three types of plastic films were UV (Ultraviolet), UV-IR (Ultraviolet and Infrared) and UV-IR-AF (Ultraviolet, Infrared and Antifog). For this study, three different experimental greenhouses developed and constructed by Institute of Agricultural Engineering ARO, the Volcani Center were used. One of the experimental greenhouses was used to investigate the effect of agro-chemical (sulfur) on the mechanical properties of cladding materials. This greenhouse had 30 identical sections. Each film was fixed on a rectangular aluminium frame. The frames were mounted on these sections. The second greenhouse was used to investigate the solar radiation transmission characteristic of plastic films. The last one was used to investigate the ageing of cladding materials in general. The experiments on the effect of sulfur evaporation on plastic films were started in June 1997 for period of 3 months. The results with sulfur evaporation on mechanical properties of PE films indicated that the elongation that take place in PE films treated with sulfur reduced about 60-80 %

Selection of the most efficient wavelength bands for 'Jonagold' apple sorting

This paper presents a method based on quadratic discriminant analysis to select the best filters for detecting a wide range of defects in 'Jonagold' apple fruit using a multi-spectral vision system. Reflectance spectra of damaged and sound tissue were recorded using a visible/NIR spectrometer. Analysed defects consisted of scald, hail damage (with and without skin perforation), limb rubs, russets, scab tissue, frost damage, rot, visible flesh damage and recent bruises. Camera filter effects were approximated by summing the reflectances of all the wavelengths within the filter bandwidth. Combinations of three and four filters were tested and evaluated for discriminating damaged tissues from healthy ones. If a three-filter combination appeared sufficient to detect most of the damaged tissue, a four-filter combination should be considered for the complete sorting automation of this bicolour apple variety. A fourth filter was necessary to quantify the ratio between the blush and ground colours. Regarding recent bruise defects which represented the major difficulty, an image segmentation algorithm based on local contrast variations can enhance their detection. (C) 2003 Elsevier B.V. All rights reserved